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Japan

Fukushima Meltdown Might Have Come With Earthquake, Not Tsunami 172

Posted by timothy
from the but-the-tsunami-helped dept.
formfeed writes "As the data from the Fukushima reactor is being reviewed it looks like the meltdown happened much earlier: '[T]he fuel rods in the No. 1 reactor were completely exposed to the air and rapidly heating five hours after the quake.' Apparently, the earthquake had caused a crack in the containment vessel. Which means, that even without the generators failing, the meltdown might still have happened. With this new data, it seems a similar incident could happen in an earthquake zone even without a tsunami."
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Fukushima Meltdown Might Have Come With Earthquake, Not Tsunami

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  • by rrohbeck (944847) on Wednesday May 18, 2011 @06:30AM (#36164008)

    If there was a crack at the bottom of the RPV, the pressure would have pushed water out rather quickly.

  • by Mindcontrolled (1388007) on Wednesday May 18, 2011 @07:32AM (#36164324)
    Yeah, that was a brainfart - I wanted to shoot for order of magnitude only, so I originally planned to set 10% of total thermal power. That somehow got garbled into 10 MW. So I undershot it by a factor of 10. You are right, with losing about 150 tons of water, the core would probably fall dry within the hour given a loss of circulation immediately after scram.
  • by antifoidulus (807088) on Wednesday May 18, 2011 @07:48AM (#36164460) Homepage Journal
    Unfortunately this isn't an isolated incident in Japan and really the only question was when, not if, something like this would happen. It's a pretty open secret that government has been in bed with TEPCO and the like for quite some time now, and that most "inspections" were mostly rubber stamp affairs. Hell, as recently as summer of 2003 there was a shutdown of a large number of reactors in the Tohoku region because it was found that managers were intentionally papering over gross safety violations. You would have thought that would have spurred the public into action, but it really did nothing.

    You also have cultural issues at play. People like to point out how there was virtually no looting after the tsunami, and rightly so, but the downside of that same culture is a lack of whistle-blowing. Japan is still in many ways a Confucian society, and as such there is very little in the way of whistle blowing. And even when there is, people tend not to believe the whistle blower over his "superiors" at work because well, they are his superiors......

    That being said, I would be willing to bet Japan goes from the rich country with the worst nuclear safety record to having one of the best. The Japanese throughout history have been a society that is very poor at initiating change, but the best at adapting to it, unfortunately it takes a huge shock for them to really change anything. Case in point, their air safety record. Japan used to have one of the worst air safety records around, but thanks to a string of major accidents in the 60s, and one huge accident(deadliest single airline crash in history) in the 80s, they now have probably the best air traffic safety records on the planet. There have been no passenger deaths in Japan since 1994, and there has only been one fatal incident involving a cargo jet. Considering the amount of air traffic both in Japan and from abroad, that is pretty damn impressive. Doubly so when you consider how small the airports are and how many flights they have to get in and out. The airline industry suffered from a lot of the same problems the nuclear industry does, rubber stamping, no whistle blowing etc. Hopefully this will serve as a wakeup call to the Japanese much in the way the major air accidents did.
  • by Anonymous Coward on Wednesday May 18, 2011 @09:38AM (#36165784)

    I've always been a big nuclear supporter of safe nuclear power, and, by safe, I mean ones where the core can reliably melt down to puddle with very minimal impact on the environment around. The thing that bothers me is that I used to believe our current nuclear plants could do this. I am no longer convinced. Indeed, I am openly concerned this is not the case.

    In the four cases of partial core meltdowns we have now seen (the Three Mile Island reactor and the three Fukushima reactors), the zicronium fuel rod casings have shown themselves to be a major liability. In all cases, they reacted with the hot steam to produce hydrogen gas, which has then posed a non-insignificant threat to the containment structure. In the case of the Fukushima reactors, we saw this actually happened to unit 3, and on day 3 of Three Mile Island incident, there was significant concern that an accumulated hydrogen bubble would explode damaging the containment structure.

    I realize that one in four (25%) is not yet enough samples to exactly pinpoint the probability of containment failure due to the explosion of accumulating hydrogen gas. However, combined with the fact this has been a major concern in all partial core meltdowns experienced so far, it is a figure we should all be concerned with. Containment failure due to hydrogen explosion is not an insignificant failure mode during meltdown, and I have yet to see it mitigated to any reasonably acceptable level.

    So, to the nuclear industry out there. Zycronium cladding for the fuel rods is currently used in pretty much every installed reactor. I realize it was chosen due to its low neutron-capture cross-section, but, in operation, it has shown itself to be a significant liability during partial meltdown. It is time to go back to the drawing board and come up with an alternative that does not have this problem. Even if that means a degradation in performance. Until I see this happening, you have lost my support.

  • Re:Uh... summary? (Score:4, Interesting)

    by jafac (1449) on Wednesday May 18, 2011 @12:46PM (#36168484) Homepage

    Well, it was also fairly obvious given the following:
    - Among the long history of safety procedure fraud at Fukushima, by TEPCO, were instances where repairs were performed using procedures that were not approved by standards, but signed off as otherwise. (therefore - plant infrastructure which may have been *designed* to withstand certain g acceleration forces of an earthquake in 1971, may not be able to withstand those forces 40 years later, after these un-approved, but fraudulently certified repairs.) - The article which mentions these variances does not provide specifics.

      - When Unit 1, and 3 exploded, the roofs of the building blew off. This indicates that the hydrogen had been generated in a reactor core at over 2200 degrees C, in the presence of water, and escaped the primary cooling system, venting into the reactor building's structure through the particle scrubbers, and exploded. A hydrogen explosion is not good, of course, but only indicative of a loss-of-cooling, at a minimum. Many experts will say that hydrogen generation is pretty much a sure sign of melting; it's not precise, but when you're in the ballpark, in a nuclear reactor, things can get very unstable very quickly, (like, milliseconds-quickly). None of these units had instrumentation, or controls, or active cooling going on. As hot byproducts are released - they have much lower melting points than the Uranium fuel, and they can migrate around, and collect in different states (or chemically react with eachother, and have a completely different set of properties - and these properties could be caustic, or explosive) . . . and cause hotspots, regions of high flux. (while some byproducts absorb neutrons and slow the reaction down). Pretty much all bets are off, as far as predicting what's going to happen.

    Strictly speaking, hydrogen generation does not mean melting HAD to happen. But in this situation, it was highly improbable that melting wasn't happening in conjunction with that.
    (and the hydrogen generation did not necessarily happen at the time of the explosions - the explosions happened later).

      - When Unit 2 exploded, the explosion blew out the side of the base of the building, through the condenser, in the primary cooling. This means that the hydrogen collected and ignited in the primary cooling system. This also means that there was enough heat in the condenser to provide ignition. This could have been due to excessive steam pressure, (compression-ignition) - with oxygen leaking IN through structural cracks. It strongly suggests that Unit 2 was damaged structurally, (the concrete torus), in the quake. It could be that thermally hot byproducts or corium caused the ignition in the RPV, maybe with an oxygen isotope (I don't know if this is possible or not, probably not), or dissasociated water,(weird isotope chemistry?) or the ignition source made it's way into the torus (which would mean, holey RPV+holey primary cooling = open core). I can't really say what the ignition source could have been, but the presence of oxygen is the crazy bit, and the simplest explanation is structural issues in the concrete (or connecting cooling pipes/valves).

    I think it was pretty idiotic and foolish (okay. . . unprofessional?) for TEPCO to state, in the immediate aftermath of the first hydrogen explosion, that they knew that the RPV was intact. They couldn't get instrument readings, or even a visual inspection for many days after that explosion to even get a half-assed confirmation of that statement. It was this kind of fumbling around and PR mismanagement that does the most damage to the industry's credibility. It would have been better for them to state what they definitely knew - what data they had, and the range of possibilities that it could have meant. That first hydrogen explosion was absolutely the time to press the panic button and evacuate residents.

The University of California Statistics Department; where mean is normal, and deviation standard.

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